A transmission method includes mapping processing, phase change processing, and transmission processing. In the mapping processing, a plurality of first modulation signals and a plurality of second modulation signals are generated using a first mapping scheme, and a plurality of third modulation signals and a plurality of fourth modulation signals are generated using a second mapping scheme. In the phase change processing, a phase change is performed on the plurality of second modulation signals and the plurality of fourth modulation signals using all N kinds of phases. In the transmission processing, the first modulation signals and the second modulation signals are respectively transmitted at a same frequency and a same time from different antennas, and the third modulation signals and the fourth modulation signals are respectively transmitted at a same frequency and a same time from the different antennas.

[Problem] According to conventional techniques, a modulation class is determined on the basis of past communication environment information stored at a base station, and the modulation class cannot be determined with consideration of a communication environment in which a signal is retransmitted. Thus, with the conventional techniques, a modulation and coding scheme cannot be determined with consideration of the communication environment in which the signal is retransmitted. [Solution] An embodiment of this communication system has a control unit that determines a first modulation and coding scheme to be applied to a signal on the basis of information about predicted first communication quality when a signal is transmitted at a first timing and information about predicted second communication quality when the signal is retransmitted at a second timing.

A method for transmitting a waveform includes adjusting first multiplexing parameters of a first multi-carrier waveform to meet communications requirements of a communications system, generating a first signal in accordance with a first input bit block and a first modulation map, placing the first signal in a first subband, wherein the first subband is specified in accordance with the first adjusted multiplexing parameters, and transmitting the first subband.

A receiving apparatus includes: a first decoder configured to decode a signal transmitted through a first layer from a layered division multiplexing (LDM) signal using a parity check matrix to generate low density parity check (LDPC) information word bits and parity bits; an encoder configured to encode the LDPC information word bits, generated by decoding the signal transmitted through the first layer, using the parity check matrix to generate parity bits corresponding only to preset columns in the parity check matrix; and a second decoder configured to decode a signal obtained by removing, from the LDM signal, a signal corresponding to the LDPC information word bits generated by decoding the signal transmitted through the first layer, the parity bits generated by the encoder, and the parity bits generated by the first decoder except the parity bits generated by the encoder, thereby to generate information word bits transmitted through a second layer.

A UE of a wireless communication network first receives a modulation and coding scheme index I.sub.MCS for demodulating a physical layer data channel of the network. The UE then demodulates the physical layer data channel with a non-square quadrature amplitude modulation (NS-QAM) having a modulation order and code rate corresponding to a spectral efficiency (SPEFF) substantially equal to a SPEFF of a square QAM (S-QAM) SPEFF indicted by the I.sub.MCS, where the NS-QAM has an effective channel code rate no larger than the code rate for which the UE may skip decoding a transport block in an initial received transmission.

Provided is a signal modulation apparatus configured to modulate an input signal into a multidimensional QAM signal using multidimensional QAM, in which Multidimensional QAM is QAM in which two-dimensional QAM is configured in a multidimensional manner using a plurality of consecutive time slots, a constellation for multidimensional QAM is part of a combination of a constellation of first two-dimensional QAM, and a constellation of second two-dimensional QAM.

A bit interleaver, a bit-interleaved coded modulation (BICM) device and a bit interleaving method are disclosed herein. The bit interleaver includes a first memory, a processor, and a second memory. The first memory stores a low-density parity check (LDPC) codeword having a length of 64800 and a code rate of 7/15. The processor generates an interleaved codeword by interleaving the LDPC codeword on a bit group basis. The size of the bit group corresponds to a parallel factor of the LDPC codeword. The second memory provides the interleaved codeword to a modulator for quadrature phase shift keying (QPSK) modulation.

Provided are a transmitter and a method for transmitting a data block in a wireless communication system. The method comprises the following steps: deciding the number of bits (s) and encoders (N.sub.ES) to allocate to one axis of a signal constellation; encoding an information bit based on the s and the N.sub.ES and generating a coded block; parsing the coded block based on the s and the N.sub.ES and generating a plurality of frequency sub-blocks; and transmitting the plurality of frequency sub-blocks to a receiver.

A transmission method includes mapping processing, phase change processing, and transmission processing. In the mapping processing, a plurality of first modulation signals and a plurality of second modulation signals are generated using a first mapping scheme, and a plurality of third modulation signals and a plurality of fourth modulation signals are generated using a second mapping scheme. In the phase change processing, a phase change is performed on the plurality of second modulation signals and the plurality of fourth modulation signals using all N kinds of phases. In the transmission processing, the first modulation signals and the second modulation signals are respectively transmitted at a same frequency and a same time from different antennas, and the third modulation signals and the fourth modulation signals are respectively transmitted at a same frequency and a same time from the different antennas.

A bit interleaver, a bit-interleaved coded modulation (BICM) device and a bit interleaving method are disclosed herein. The bit interleaver includes a first memory, a processor, and a second memory. The first memory stores a low-density parity check (LDPC) codeword having a length of 64800 and a code rate of 7/15. The processor generates an interleaved codeword by interleaving the LDPC codeword on a bit group basis. The size of the bit group corresponds to a parallel factor of the LDPC codeword. The second memory provides the interleaved codeword to a modulator for quadrature phase shift keying (QPSK) modulation.